Field of the Invention
The present invention relates to a radiation imaging apparatus, a radiation imaging system, and a control method of the radiation imaging system.
Description of the Related Art
There is a radiation imaging apparatus including a pixel array in which pixels each including a conversion element configured to convert radiation into charges, and a switching element such as a thin-film transistor are arrayed. Recently, multi-functionality of radiation imaging apparatuses of this type is examined. As one of these functions, incorporation of an automatic exposure control (AEC) function is receiving attention. Automatic exposure control in the radiation imaging apparatus can be used for, for example, detection of the start of irradiation with radiation from a radiation source, decision of the timing to stop irradiation with radiation, and detection of the dose or accumulated dose of radiation.
Japanese Patent Laid-Open No. 2012-247354 discloses a radiation image detection apparatus that detects the start and end of irradiation with radiation by monitoring an output from a high-sensitivity detection element selected in advance from a plurality of detection elements arranged in an imaging region where a plurality of pixels are arrayed. The detection of the end of irradiation with radiation in the radiation image detection apparatus disclosed in Japanese Patent Laid-Open No. 2012-247354 is detection of the timing when irradiation with radiation ends, and is not detection of the timing to end irradiation with radiation. The radiation image detection apparatus disclosed in Japanese Patent Laid-Open No. 2012-247354 monitors an output from a preselected high-sensitivity detection element, that is, a specific detection element, and cannot detect the exposure state of a portion (for example, a soft tissue or bone) regarding diagnosis. For example, when radiation entering a detection element whose output is monitored enters the detection element without passing through an object, the exposure state of a portion regarding diagnosis in the object cannot be detected depending on monitoring of an output from the detection element.